1. Field of the Invention
The present invention relates to a white light emitting device, and more particularly, to a monolithic white light emitting device capable of spontaneous white light emission.
2. Description of the Related Art
Generally, white light emitting devices generate white light using light emission by a semiconductor and light emission by a phosphor (see U.S. Pat. Nos. 6,069,440 and 5,998,925). These light emitting devices absorb light emitted by the semiconductor using the phosphor, so emits light close to white. The semiconductor usually emits blue light, and the phosphor absorbs the blue light emitted by the semiconductor to generate green/red light. Hence, the phosphor is a mixture of green and red fluorescent materials.
According to a hybrid white light emitting device having such a structure, it is not easy to implement an integrated circuit manufactured according to an existing semiconductor manufacturing process. Thus, the fields to which the hybrid white light emitting device are applied is restricted.
T. Mukai has proposed a white light emitting device (LED) having no phosphors and using multi-band emission (see JJAP 41 (3A) L246 2002). Accordingly, Mukai's LED has a plurality of active layers to generate light of different wavelengths.
This LED, which is usually used in a backlight device, needs to be easily manufactured and to have high light-emission efficiency and whiteness.